What I saw on the video did look excessive, but I think it was more of a result of there being an excessive amount of cops out during the marathon than it did racism.
I think the fact that they were called to that specific area due to a disgruntled homeowner can be pinned on racism. Some rich Newton homeowner upset about the Boston Marathon party being thrown in front of their house calls the police and says people are being unruly, running on the course, blah blah - whatever she/he had to say to get the cops to pay attention. I don't know how you can live on the Boston Marathon course and not be understanding of the excessive partylike atmosphere of the day. You want to have a racism question, you should be asking: "would that homeowner have called the cops if the group was a bunch of white college students?"
Regardless, Newton PD receives the complaint(s), and the dispatcher than radios it in to the cops in the area, and the cops in the area drive to the home.
They have an excessive amount of cops out along the course in Newton. They're all just standing/sitting around with nothing to do. When they got an actual call with something to do, they probably all just jumped on it and showed up.
They weren't handcuffing or shoving the people into the pavement or anything. They were just now all standing around in that area with a kind of "well, I guess we're here now" look.
So I think it looked bad that a ton of cops showed up, but it wasn't like they radioed into the station and sent out a swat team and called in cops from surrounding towns to assist. A bunch of bored cops probably just rode over a block or two to see what was going on.
I think if you want to point the finger at someone here, you point it at the homeowner who was annoyed enough to call it in vs. the cops who happened to be there, or the BAA who had really nothing to do with anything here.